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Biomedical subjects

W Stremmel

Publications and source records attributed to W Stremmel.

At least 109 records · Page 6Linked to original sources
PubMed1998

Electrogenicity of hepatocellular fatty acid uptake.

Sensitivity of cellular fatty acids uptake to the membrane potential difference is still a matter of controversy. For direct evaluation of potential sensitivity the effect of changing membrane potential on uptake of a fluorescent long chain fatty acid derivative, 12-NBD-stearate, in isolated rat hepatocytes, was examined. Changes in membrane potential were achieved by patch clamp procedures. Fatty acid influx was simultaneously determined by recording of cell fluorescence. Hyperpolarization from -30 to -70 mV accelerated fatty acid influx whereas depolarization to +50 mV reduced uptake. After obtaining equilibrium hyperpolarization increased cell fluorescence, whereas depolarization pushed NBD-stearate out of cells. Potential sensitivity of uptake was dependent on the fatty acid concentrations in the medium with most prominent effects at low unbound concentrations. These data show that, at low fatty acid concentrations, uptake is, in part, driven by an intracellular negative electric membrane potential.

4-Chloro-7-nitrobenzofurazan↗
PubMed1998

18F-labeled fluorouracil positron emission tomography and the prognoses of colorectal carcinoma patients with metastases to the liver treated with 5-fluorouracil.

BACKGROUND: Although many factors have been investigated in connection with the prognoses of colorectal carcinoma patients with metastases to the liver, a means for evaluating response and prognosis prior to the administration of standard chemotherapy has not been available. Positron emission tomography (PET) is a noninvasive means of measuring the distribution of radiolabeled cytostatic agents in tumor regions. METHODS: Prior to the administration of 5-fluorouracil chemotherapy, the authors examined 14 colorectal carcinoma patients with unresectable liver metastases using a single PET scan and 18F-labeled fluorouracil (18F-FU). Clinical response and survival time were correlated with 18F-FU uptake values (SUV) measured in liver metastases 120 minutes after tracer infusion. RESULTS: Trapping of 18F-FU varied even among different metastases in the same patient. The range of SUV was 0.9-4.3 (mean, 2.20). Four patients with SUV exceeding 2.8 had stable disease for longer than 12 months and survived longer than 21 months. Three patients with SUV less than 1.2 had progressive disease and survived less than 12 months. The 6 patients with partial remission or stable disease had a mean SUV of 2.96 and a mean survival of 31.6 months. Eight patients with progressive disease had a mean SUV of 1.59 and a mean survival of 14.5 months (Student's t-test, P < 0.012). In scatterplot analysis, there was a statistically significant correlation between SUV and survival time. CONCLUSIONS: Patients with high 18F-FU uptake values are more likely to achieve at least stabilization of disease with planned chemotherapy. 18F-FU PET may be a valuable new tool for determining, prior to 5-FU-based chemotherapy, which patients are likely to have good responses and prolonged survival.

Aged↗
PubMed1998

Indication for a specific interaction of fatty acids with a liver sinusoidal plasma membrane carrier.

To evaluate whether fatty acids interact specifically with plasma membrane proteins, binding of [3H]oleate to rat liver plasma membranes was determined after exposure of the plasma membranes to temperatures of 40 to 95 degrees C for 15 min. Starting at 50 degrees C, membrane binding of [3H]oleate gradually decreased, reaching at 95 degrees C a 58.2% inhibition of binding compared to control values obtained at 18 degrees C. Another criterion of specific interaction with a membrane transport protein was the observation that two different long chain fatty acids, palmitate and oleate, compete for uptake in the experimental system of the isolated perfused rat liver. Both observations support the hypothesis that hepatocellular uptake of fatty acids represents a carrier mediated transport mechanism and not simple diffusion.

Animals↗
PubMed1998

Incidence, prevalence, and clinical outcome of hepatitis GB-C virus infection in liver transplant patients.

A novel RNA virus of the Flaviviridae family has been discovered recently and designated hepatitis GB-C virus (GBV-C). Previous studies have reported that GBV-C is associated with posttransfusion hepatitis, chronic viral hepatitis, and cryptogenic hepatitis. However, the clinical significance of GBV-C infection has been questioned increasingly in patients not undergoing transplantation. To investigate whether GBV-C infection under immunosuppression affects the clinical or the histological outcome in liver transplant recipients, we determined the prevalence and incidence of GBV-C infections and the clinical and histological signs in patients after orthotopic liver transplantation (OLT). The presence of GBV-C was tested in sera from patients before and in regular intervals up to 6 years after OLT by nested reverse transcription-polymerase chain reaction using primers derived from the NS3 region. A total of 72 patients were studied. Before OLT, 8 of 72 (11.1%) patients were positive for GBV-C. After OLT, 7 of 8 (87.5%) remained positive. Of 64 patients who were negative for GBV-C before OLT, 23 became positive after OLT, resulting in a de novo rate of GBV-C infection of 35.9%. We could not detect a higher rate of histologically proven hepatitis in GBV-C-positive patients (29.1%) than in GBV-C-negative patients (14.6%, P > 0.057). Comparing GBV-C-positive with GBV-C-negative liver transplant patients, we could not find any differences in age, gender, liver function tests, number of blood transfusions, histological degree of hepatitis, or number of rejection episodes. Survival was not negatively influenced by GBV-C positivity. In conclusion, the presence of GBV-C did not influence the clinical or histological outcome in liver transplant patients.

Adult↗
PubMed1998

Long-chain fatty acid uptake by skeletal myocytes: a confocal laser scanning microscopy study.

Studies of regulation of free fatty acid (FFA) utilization by skeletal muscles have focused on plasma FFA delivery and on intracellular factors affecting FFA metabolism. The present study was conducted to directly analyse the uptake process of fatty acids into single myocytes. Cells were isolated from the rat flexor digitorum brevis muscle. Confocal laser scanning microscopy was utilized to analyse the uptake of the fluorescent fatty acid derivative 12-NBD-stearate, which is not metabolized by muscle tissue. Uptake represented a saturable function of the unbound fatty acid concentration in the medium (K(m) 366 +/- 118 nM, Vmax 2.1 +/- 0.3 AU/s) and depended on the medium sodium concentration. Reduced buffer pH increased initial uptake rates, whereas lactate (10 mM) had no effect. Membrane hyper- and depolarization decreased uptake rates. This study demonstrates for the first time kinetic data from isolated myocytes with evidence for a carrier-mediated transport mechanism for long-chain fatty acids.

4-Chloro-7-nitrobenzofurazan↗
PubMed1998

Accelerated schedule of hepatitis B vaccination in liver transplant candidates.

Liver transplantation has become the treatment of choice worldwide for many patients with end-stage liver disease. In terms of survival and quality of life, the results of the procedure in many centers are very good. However, the long-term function of the grafts may be affected by vascular, immunologic, or infection problems, the latter being a major cause of morbidity and mortality after orthotopic liver transplantation (OLT). Therefore, prophylactic vaccination against hepatitis B virus (HBV) infection is recommended in patients awaiting liver transplantation. Individuals with chronic advanced liver disease are known to be less responsive to HBV vaccination. On the other hand, the widely recommended standard schedule (months 0, 1, and 6) for immunization against hepatitis B takes 6 months, a regimen which may not be completed in time prior to OLT or which may not be completed due to noncompliance, possible reasons for the lower rates of seroprotection in OLT candidates. Studies show that, in principle, complete immunization with an accelerated hepatitis B vaccination protocol (0, 7, 21 days) induces early seroprotection with excellent seroprotection rates and anti-HBs titers in immunocompetent individuals. We therefore performed a prospective clinical trial to assess immunogenicity and reactogenicity of this accelerated vaccination regimen in OLT candidates compared to healthy controls.

Female↗
PubMed1998

Effect of tauroursodeoxycholic acid on bile-acid-induced apoptosis and cytolysis in rat hepatocytes.

BACKGROUND/AIMS: In cholestatic liver disease, bile acids may initiate or aggravate hepatocellular damage. Cellular necrosis and cell death may be due to detergent effects of bile acids, but apoptosis may also play a role. In cholestasis, the conditions determining either apoptotic or cytolytic cell death are still unclear. Primary rat hepatocytes in culture represent a suitable model to study bile-acid-induced liver damage. METHODS: Glycochenodeoxycholic acid, a hydrophobic bile acid, was used to induce cell damage. Tauroursodeoxycholic acid, a hydrophilic bile acid, served as substrate to study possible protective effects of such compounds. To study the time and concentration dependency of bile-acid-induced cytolysis and apoptosis, morphologic alterations, hepatocellular enzyme release and nucleosomal DNA fragmentation were evaluated. RESULTS: Bile-acid-induced cytolysis, as indicated by hepatocellular enzyme release and by morphologic signs of membrane destruction, increased with concentration and time. Addition of tauroursodeoxycholic acid to the incubation medium reduced cytolysis significantly, indicating a direct hepatoprotective effect of this bile acid against the detergent action of hydrophobic bile acids. In contrast to cytolysis, apoptosis with DNA fragmentation was induced by low concentrations of glycochenodeoxycholic acid a few hours after incubation. Coincubation with tauroursodeoxycholic acid in equimolar concentrations significantly reduced apoptosis, indicating another direct hepatoprotective effect of tauroursodeoxycholic acid. CONCLUSIONS: It seems likely that in severe cholestasis, bile-acid-induced injury of hepatocytes is due mainly to cytolysis, whereas in moderately severe cholestasis apoptosis represents the predominant mechanism of bile acid toxicity. Tauroursodeoxycholic acid may reduce both bile-acid-induced apoptosis and cytolysis.

Animals↗
PubMed1998

Hepatic failure and liver cell damage in acute Wilson's disease involve CD95 (APO-1/Fas) mediated apoptosis.

Wilson's disease can result in fulminant liver failure due to hepatic copper overload. The CD95 system mediates apoptosis and has been demonstrated to be involved in liver disease. In this study CD95 mediated apoptosis was investigated in patients with fulminant hepatic failure in the course of Wilson's disease and in an in vitro model of copper treated human hepatoma cells. In patients, hepatic expression of CD95 and CD95L mRNA and apoptosis were detected. Copper overload in vitro resulted in hepatocytic apoptosis which could be reduced with a neutralizing anti-CD95L antibody. Copper treatment of hepatocytes results in activation of the CD95 system and induction of apoptosis which is operative during the course of hepatic failure in acute Wilson's disease.

Acute Disease↗
PubMed1998

Induction of tumour necrosis factor (TNF) receptor type p55 and p75 in patients with chronic hepatitis C virus (HCV) infection.

There is evidence that TNF-alpha contributes to the pathogenesis of chronic viral hepatitis. The cellular effects of this cytokine are regulated by two specific receptors, and membranous shedding of these receptors reflects activation of the TNF system. We performed a study of TNF-alpha and functionally active soluble TNF-receptors (TNFR-p55 and -p75) in 105 patients with chronic HCV infection. In HCV RNA-positive patients a significant enhancement of TNF-alpha and both receptor types was observed compared with controls (TNF-alpha 83.8+/-91.7 pg/ml versus 18.8+/-8.4 pg/ml, P<0.001; TNFR-p55 1.4+/-0.4 ng/ml versus 0.9+/-0.2 ng/ml, P<0.0001; TNFR-p75 6.4+/-2.4 ng/ml versus 2.9+/-0.6 ng/ml, P<0.0001, respectively). The enhanced serum levels of TNF-alpha and TNFRs were reflected by a significant expression of TNFR-specific mRNA in peripheral mononuclear cells of HCV-infected patients (P<0.001). Serum aminotransferases correlated with soluble TNFR-p75 (P<0.001) but not with TNFR-p55 and TNF-alpha. We demonstrated an association of the degree of histological inflammation with both TNFRs (P<0.01). Furthermore, enhanced hepatocellular expression of TNF-alpha and TNFRs could be demonstrated by immunohistochemical staining in HCV-infected patients. Sixty-eight out of 105 patients were treated with interferon-alpha (IFN-alpha) (3x10(6)U x 3/week). Pretreatment levels of TNF-alpha and TNFRs did not differ between responders and non-responders. Our results demonstrate that TNF-alpha and TNFRs are enhanced in chronic HCV infection and reflect histological activity of the disease. This up-regulation of TNFRs might modify host response and potentially contribute to liver damage in chronic HCV infection.

Adult↗
PubMed1998

Effect of S-adenosylmethionine versus tauroursodeoxycholic acid on bile acid-induced apoptosis and cytolysis in rat hepatocytes.

BACKGROUND: S-adenosylmethionine (SAMe) increases survival in alcoholic liver cirrhosis and may have a beneficial effect in cholestatic liver disease. SAMe repletes glutathione stores and protects tissue from oxygen free radicals. The effect of SAMe on bile acid-induced apoptosis is unknown. In the present study the possible hepatoprotective effect of SAMe was evaluated and compared with that of tauroursodeoxycholic acid (TUDCA). METHODS: Primary rat hepatocytes treated with glycochenodeoxycholic acid (GCDCA) were used as a model for cholestasis-induced hepatocellular damage, which served to study the effects of SAMe and TUDCA on bile acid-induced apoptosis and cytolysis. RESULTS: SAMe reduced bile acid-induced apoptosis but did not prevent bile acid-induced cytolysis. Compared with SAMe, TUDCA was more efficient in reducing apoptosis due to toxic bile acids. The combination of SAMe and TUDCA had additive effects in reducing apoptosis. CONCLUSION: The reduction in bile acid-induced apoptosis by SAMe may represent one of the factors responsible for its beneficial effects in the treatment of liver diseases.

Animals↗
PubMed1998

Clinical impact of GB-C virus in haemodialysis patients.

BACKGROUND: Haemodialysis patients run a high risk of acquiring viral hepatitis B (HBV) or C (HCV) infection. Recently a new parenterally transmittable RNA virus, designated GBV-C, was isolated. METHODS: We therefore screened 266 patients on maintenance dialysis and 358 blood donors as a control group for GBV-C by nested PCR and correlated the data with AST, ALT, duration of dialysis, transfusions, renal transplants and coinfections with HBV and HCV. RESULTS: The prevalence of GBV-C among haemodialysis patients was 7.9%, and 3.6% among blood donors. Neither duration of dialysis nor number of blood transfusions were associated with GBV-C infection, whereas GBV-C-positive patients were significantly more often transplanted than GBV-C-negative individuals. Transaminases of GBV-C-positive individuals remained within normal limits in all haemodialysis patients and normal in all infected blood donors. Coinfections of GBV-C with HBV and HCV were only present in 0.7% and 1% respectively. CONCLUSIONS: We conclude that GBV-C virus infection is frequent among haemodialysis patients. Transaminases cannot serve as surrogate markers, and parenteral as well as community-acquired infection seems to be possible.

Adolescent↗
PubMed1998

Diversity of Helicobacter pylori vacA and cagA genes and relationship to VacA and CagA protein expression, cytotoxin production, and associated diseases.

The vacuolating cytotoxin and the cytotoxin-associated protein, encoded by vacA and cagA, respectively, are important virulence determinants of Helicobacter pylori. Sixty-five H. pylori strains were isolated from dyspeptic patients (19 with peptic ulcer disease, 43 with chronic gastritis, and 3 with gastric cancer) and studied for differences in the vacA and cagA genes and their relationship to VacA and CagA expression, cytotoxin activity, and the clinical outcome of infection. By PCR, fifty-four (83.1%) of 65 strains had the vacA signal sequence genotype s1 and only 10 (15.4%) had the type s2. After primer modification, the vacA middle-region types m1 and m2 were detected in 24 (36.9%) and 41 (63.1%) strains, respectively. The combinations s1-m2 (31 [47.7%]) and s1-m1 (23 [35.4%]) occurred more frequently than s2-m2 (10 [15.4%]) (P = 0.01). No strain with the combination s2-m1 was found. All 19 patients with peptic ulcers harbored type s1 strains, in contrast to 32 (74.4%) of 43 patients with gastritis (P = 0.02). The vacA genotype s1 was associated with the presence of cagA (P < 0.0001), VacA expression (P < 0.0001), and cytotoxin activity (P = 0.003). The cagA gene was detectable in 48 (73.8%) of 65 isolates and present in 16 (84.2%) of 19 ulcer patients and 29 (67.4%) of 43 patients with gastritis (P = 0.17). The vacA genotypes of German H. pylori isolates are identical to those previously reported. H. pylori strains of vacA type s1 are associated with the occurrence of peptic ulceration and the presence of cagA, cytotoxin activity, and VacA expression.

Antigens, Bacterial↗
PubMed1998

Antiviral potential of interferon-omega on hepatitis B virus replication in human hepatoma cells.

Interferon-alpha (IFN-alpha) and other cytokines are able to interfere with hepatitis B virus (HBV) replication. However, a sustained antiviral effect is achieved only in 25% to 40% of the patients with chronic HBV infection and clearance of the virus rarely occurs, stressing the need for developing therapeutic alternatives. In this study the antiviral potential of a new recombinant interferon, IFN-omega was investigated. IFN-omega was assessed in comparison with IFN-alpha 2c, IFN-gamma, and TNF-alpha with respect to production of HBV proteins and DNA in HepG2.2.15 cells, a HBV-DNA transfected hepatoma cell line which produces infectious viral particles. Cells were seeded at different states of confluence (20%-90%) and treated with increasing concentrations of interferons (5 to 5,000 U/ml), TNF-alpha (5 to 500 ng/ml), or combinations of both for one to three days. IFN-omega reduced the production of HBsAg down to 59% of the untreated controls, which was comparable to the reduction obtained by treatment with IFN-alpha (60%), the standard interferon used for the treatment of chronic HBV infections. The strongest inhibition, however, was achieved by treatment with 500 ng/ml TNF-alpha (42%). Likewise, production of HBeAg and synthesis of HBV DNA were inhibited to similar degrees by the different interferons. In non-replicating high-density cultures only TNF-alpha was effective. IFN-omega is of similar antiviral potential as IFN-alpha in this in vitro experimental system.

Animals↗
PubMed1998

The role of p53 and the CD95 (APO-1/Fas) death system in chemotherapy-induced apoptosis.

To explore the pathway of p53 dependent cell death, we investigated if p53 dependent apoptosis following DNA damage is mediated by the CD95 (APO-1/Fas) receptor/ligand system. We investigated cell lines of solid human tumors upon treatment with clinically relevant chemotherapeutic drugs known to act via p53 accumulation. Treatment with these cytotoxic drugs led to an upregulation of both, the CD95 receptor (CD95) and the CD95L (CD95L). Induction of the CD95L occurred in p53 wild-type (wt), p53 mutant (mt) and in cell lines lacking p53 altogether (p53-/-). Thus, the regulation of the CD95L in response to chemotherapeutic drugs clearly involves p53 independent mechanisms. Most importantly, upregulation of CD95 occurred only in cell lines with wild-type p53, thereby strongly increasing the responsiveness towards CD95 mediated apoptosis. Thus, upregulation of the CD95 receptor seems to be dependent on intact wild-type p53. Apoptosis was mediated by cleavage of the receptor proximal caspase, caspase-8 (FLICE/MACH). Caspase-8 cleavage was observed, independent of the p53 status of the tumor cells and irrespective whether or not apoptosis was dependent on the CD95 system. Hence, additional effector pathways besides CD95/CD95L signaling are likely to contribute to drug-induced apoptosis.

Antineoplastic Agents↗